Spark-plug.



A. HELWIG.

SPARK PLUG. APPLIGATION FILED FEB. 23, 1909.

Patented Nov. 16, 1909.

4 M m F 2 g n W g m R %/w 6 0% ALFRED HELWIG, OF DETROIT, MICHIGAN;

SPARK-PLUG.

nausea.

Specification of Letters Patent. Patented NOV. 16,1909.

- Applicationfiled February 23, 1909. Serial No. 479,526.

To all whom it may concern. I

Be it known that I, ALFRED llELX-IG, a citizen of the United States of America, reldlllg at Detroit, in the county of lVayne and State of Michigan", have invented certain new and useful Improvements in Spark Plugs, of which the following is a specification, reference being bad therein to the accompanying drawings.

This invention relates to spark plugs for the ignition systems of explosive engines and more especially to certain improvements therein whereby a double spark gap is provided and whereby the parts may be so adjusted as to give a substantially single spark gap if desirech V The invention consists in the matters hereinafter set forth, and more particularly pointed out in the appended claims.

In the drawings, Figure 1 is a view in lon- Q gitudinal section of a spark plug embodying features of the invention. Fig. 2 is a view of the inner terminal end thereof. Fig. 3 is a view in longitudinal section of the lower terminal end showing the parts adjusted for producing a single spark. Fig. 4 is a View in transverse section on line of Fig. 1

. through a bridge.

. the

Referring to the drawings, an outer shell 1 exterlorly screw-threaded or otherwise fitted for insertion in the wall of amotors' combustion chamber, has a terminal 2 ex tending from its inner end. An insulating bushing 3, preferably of mica or fiber disks placed on an axial stem l, has an enlarged center portion 5 by which it is secured in the shell 1, the latter being suitably counterbored and provided with a clamping nut 6, parts being so disposed that by releasing saidniut the bushing'may be adjusted rotatably in the shell. The bushing .3 is considerably longer than the shell 1 and the inner end of the latter is countersunk or provided with an enlarged opening forming an air space 7 around the bushing. A head 8 on the inner end of the stem 4 has a terminal 9 extending toward the shell and so disposed that when turned into register or alinement with the terminal 2 it approaches the latter quite closely and forms an air gap therewith as indicated in Fig. 3. A metal ring 10 is secured on the bushing 3 intermediate the ends of the two terminals with which it forms air gaps. The usual binding post arrangement 12 is provided at the outer end' of the stem.

In operation, with normal conditions in the generator for the system for whichthe plug isused thoclectrodes are disposed d1- ametrically as in Fig. 1, the two alr gaps forming the double j innp sparks as required. If for any reason the current weakens, the

elegtrodes may be turned into position indi-,

cated in Fig. 3, whereby a Wide spark is readily produced, the short air gap between the electrodes together with the proximity of the metal bridge 10 forming an interval which is readily crossed by a current of comparatively low tension.-

Obviously, changes in the details of construction may be made, and I do not care to limit myself to any particular form or arrangement of parts.

What I claim as my invention is l. A spark plug comprising an outer shell having a spark terminal on its lower end, an

insulated rotatable central stem adjustably secured in the shell having a terminal adapted to form a spark gap with the shell ter minal when proximate thereto, and an annular insulated bridge on the stem-forming a spark gapwith each terminal.

2. A spark plug comprising an outer shell, a spark terminal extending from the lower end thereof, an insulated rotatable central stem adjustably secured in the shell, a

terminal on the stem adapted to form, a-

spark gap with the shell terminal when proximate thereto, and'an annular insulated bridge on the stem forming spark gaps with the terminals.

3. A spark plug comprising an outer shell having a spark terminal on'one end thereof, an insulting bushing rotatably adjustable in the shell, an axial stem in the bushing having a spark terminal on the end adj aoent the shell terminal, adapted to form a spark gap therewith 'wlien proximate thereto, and an annular bridge on the bushing forming a spark gap with'each terminal.

4. A spark plug comprising an outer shell having a spark terminal on its inner end, an insulating bushing rotatably adjustable in the shell whose inner end. extends past the shell terminal, an axial stem in the bushing having a terminal on its inner end adapted to form a spark gap with the shellterminal when proximate thereto, and an annular bridge on the bushing between and concentrio with .the two terminals with which it forms spark gaps. v

5. A spark plug comprising an outer shell,

an. insulating bushing extending therethrough having an enlarged portion mediate its ends seated on a counterbore of the stem, a clamping nut adjustably securing the bushin the inner end of the shell having an en ar'ged bore forming an air gap around the proximate portion of the bushing, a terminal on the inner end of the shell, an axial stem extending through the bush- 0 ing, a terminal on the inner end thereof adapted when in register with the shell terminal to form an air gap therewith,'and a metal annular bridge on the bushing adapted to form an air gap with both terminals.

In testimony whereof I afiix my signature 15 in presence of two witnesses.

ALFRED HELNIG. Witnesses:

ANNA M. Donn, ANNA M. SHANNON. 

